There's no doubt that Nvidia's GeForce GTX 680 has proven itself to be a serious performance contender and although we don't know what Nvidia is planning below the GTX 680, the company did also announce its range of mobile GPU's alongside it. The GeForce 600M series will at least initially consist of 10 new GPU's, of which three are high-end GTX models.

There's no doubt that Nvidia's GeForce GTX 680 has proven itself to be a serious performance contender and although we don't know what Nvidia is planning below the GTX 680, the company did also announce its range of mobile GPU's alongside it. The GeForce 600M series will at least initially consist of 10 new GPU's, of which three are high-end GTX models.

The "standard" models can be seen in the table below and ranges from the very basic GeForce 610M to the GT 650M. There are some oddities here though and they're not that easy to spot given the model names. The GeForce 610M, GT 620M, GT 630M and GT 635M are in fact not based on the Kepler architecture, but rather the older Fermi architecture. However, Nvidia is said to be making these new mobile chips using TSMC's 28nm manufacturing process, to the actual GPU's should be smaller and cooler running that the mobile GeForce 500-series of GPU's.

As for the new Kepler based GPU's, all three GT models have 384 shaders/CUDA cores and a 128-bit memory interface. First up we have the GT640M LE which is a slower clocked GT 640M which for some reason features much lower memory bandwidth than the GT 640M, despite that the GT 640M LE has an equally wide 128-bit memory bus. Rumour has it that at least some GT 640M LE cards will be re-branded Fermi based GPU's, but we're uncertain if this is actually the case or not and it's not something we've heard anything about.

Besides clocks speeds and memory bandwidth the GT 640M LE and the GT 640M appears to be identical and there's little else to see here. The faster GT 650M is again another very similar part, although in this case Nvidia has provided specific clock speeds for the GPU depending on the memory type it's paired up with. When DDR3 is being used with the GT 650M it will be clocked at 850MHz, but if GDDR5 is being used, then the GPU will be clocked at 735MHz. The other GPU's only feature an "up to" GPU clock speed, so it's pretty clear from this that Nvidia doesn't want the GT 650M to compete with its higher-end parts.

The high-end parts start with the GeForce GTX 660M and this is the first part that only supports GDDR5 memory. On a hardware level it appears to be identical to the GT 650M with 384 shaders and a 128-bit memory interface. However, the GPU is clocked higher at 835MHz and it's likely that it'll be paired with faster memory in most scenarios, although it has the same theoretical peak memory bandwidth as the GT 650M. On feature that comes into play here though is SLI support, as only the GTX models support SLI, albeit we're not sure how many notebook makers would opt to offer a machine with a pair of upper mid-range cards in SLI.

This brings us to the GTX 670M and GTX 675M which are simply re-branded Fermi chips that used to be known as the GTX 570M and GTX 580M. The GTX 670M features slightly higher clock speeds than the GTX 570M, but this isn't likely to have a huge impact on game performance. The GTX 675M is identical to the GTX 580M, despite Nvidia's attempt at confusion on its own website by listing the shader clock for the older GPU's and the core clock for the rebranded models.

Nvidia has of course provided scores of benchmarks and other figures to back up its new and re-branded GPUs and if you hit the source link you'll find all of those. The only problem is that most of them aren't comparable in any sensible way. What we don't doubt is Nvidia's claim that its new GeForce GT 640M is twice as efficient as a GTX 285M from 2010, yet fitting in much slimmer notebooks. In fact, the example Nvidia is giving shows the GT 640M in an Acer Timeline Ultra M3 Ultrabook and we also know that Gigabyte is planning on using the same GPU in its upcoming Ultrabooks.